Archive for the ‘macro photography’ Category

Stenogomphurus rogersi exuvia

February 24, 2018

Bob Perkins collected an unknown species of clubtail larva in February 2017 from a stream located in either Carroll- or Grayson County, Virginia USA. The larva emerged from one of Bob’s holding tanks on 13 March 2017 and metamorphosed into an adult female Sable Clubtail dragonfly (Stenogomphurus rogersi).

A two-step process was used to verify the genus and species of the exuvia.

  1. Determine the family.
  2. Determine the genus and species.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video, Identifying dragonfly larva to family (8:06). Here’s the decision tree used to identify the exuvia as a member of the Family Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like). [See Photo No. 2.]
  • Antennae are club-like (not thin and thread-like, as in Aeshnidae). [See Photo No. 1.]
  • Eyes not exceptionally large compared to the size of the head (not large, as in Aeshnidae). [See Photo No. 1.]
(See a full-size version of the original photo, without annotation.)

The white filaments that extend from the split in the thorax (as shown above) are breathing tubes, artifacts of the unique respiratory system of dragonfly nymphs.

Step 2. Genus and species

Gomphidae is the second largest family of dragonflies, so it can be challenging to identify some specimens to the genus and species level.

The dichotomous key for Gomphidae larvae that appears on p. 233 in Dragonflies of North America, Third Edition by Needham et al. was used to verify the genus and species of the exuvia.

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

The first couplet [1, 1′] is as follows.

1. Median premental tooth lower than surrounding setae (Fig. 271b); small dorsal hooks present on abdominal segments 8 and 9; lateral spines present on segment 6 (Fig. 272) [rogersi]
1’. Median premental tooth as high as surrounding setae (Fig. 271a); dorsal hooks absent or vestigial on abdominal segments 8 and 9; lateral spines usually absent on segment 6 (Fig. 272) [consanguis]

The following annotated image shows a ventral view of the prementum. Notice the median premental tooth is lower than the surrounding setae.

(See a full-size version of the original photo, without annotation.)

The next annotated image shows a dorsal view of the distal abdomen. A leap of faith is required to see the small dorsal hooks present on abdominal segments eight and nine (S8, S9), but they are there. Also notice the lateral spines present on segment six (S6).

(See a full-size version of the original photo, without annotation.)

Therefore this specimen is confirmed as an exuvia from Stenogomphurus rogersi. Further, the rudimentary ovipositor shown in Photo No. 4 indicates this individual is a female.

(See a full-size version of the original photo, without annotation.)

Bonus Gallery

No. 5 | Sable Clubtail (Stenogomphurus rogersi) | exuvia (head-dorsal)

The Stenogomphurus rogersi exuvia is ~3.0 cm (~1.2 in) long.

No. 6 | Sable Clubtail (Stenogomphurus rogersi) | exuvia (dorsal-lateral)

(See a full-size version of the original photo, without annotation.)

Adult Sable Clubtail dragonflies are slightly larger, on average 4.7 – 5.0 cm (~1.9 – ~2.0 in) long.

Image used with permission from Bob Perkins.

This individual is a female, as indicated by her rounded hind wings and terminal appendages.

Image used with permission from Bob Perkins.

Tech Tips

The following equipment was used to shoot Photo No. 1, 4, 5 and 6: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens(set for manual focus); and Canon MT-26EX-RT Macro Twin Lite. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for some photos. Photo No. 2 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification); and Canon MT-26EX-RT Macro Twin Lite.

Adobe Photoshop CC 2017 was used to annotate selected images.

Bob Perkins’ photos, taken soon after emergence, were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Related Resource: Miraculous metamorphosis, a blog post featuring a head-to-head juxtaposition of the same exuvia and dragonfly that are the subjects in this post.

Copyright © 2018 Walter Sanford. All rights reserved.

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Miraculous metamorphosis

February 22, 2018

It’s hard to believe an odonate larva that looked like this…

…transformed into the adult dragonfly shown below.

Image used with permission from Bob Perkins.

The Backstory

Bob Perkins, a good friend and fellow Virginian, has been collecting and rearing odonate larvae since 01 January 2017. Bob’s success rate is extraordinarily high, meaning most of the larvae he collects live to emerge as adults.

Bob collected an unknown species of clubtail larva in February 2017 from a stream located in either Carroll- or Grayson County, Virginia USA. The larva emerged from one of Bob’s holding tanks on 13 March 2017 and metamorphosed into an adult female Sable Clubtail dragonfly (Stenogomphurus rogersi).

Amateur- and professional scientists collect and rear odonate larvae in order to observe the adult species that emerge. Then it is possible to reverse-engineer the morphological characters that enable identification of specific species of larvae. An upcoming blog post will feature information about how to identify Sable Clubtail larvae/exuviae.

Tech Tips

The first image is a composite of nine (9) photos taken using the following equipment: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 3x magnification); and Canon MT-26EX-RT Macro Twin Lite.

Adobe Photoshop CC 2017 was used to focus stack the photos and post-process the final output.

The second image was taken by Bob Perkins, soon after emergence, using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Related Resource: Stenogomphurus rogersi exuvia, a blog post that describes how to identify Sable Clubtail dragonfly larvae/exuviae.

Copyright © 2018 Walter Sanford. All rights reserved.

Post update: Cordulegastridae exuvia

February 16, 2018

In a recent blog post entitled Cordulegastridae exuvia, I was able to identify the specimen to the family level. Since then, I was able to identify the genus and species.

The dichotomous key for Cordulegastridae larvae that appears on p. 330 in Dragonflies of North America, Third Edition by Needham et al. was used to identify the exuvia.

dichotomous key: a key for the identification of organisms based on a series of choices between alternative characters. Source Credit: Merriam-Webster Dictionary.

The first couplet [1, 1′] is as follows.

1. No lateral spines on abdominal segments 8-9; western [2]
1’. Lateral spines present on segments 8-9; eastern [3]

No. 1 | Cordulegaster sp. | exuvia (ventral)

(See a full-size version of the original photo, without annotation.)

Since the preceding annotated image shows lateral spines on abdominal segments eight and nine (S8, S9), proceed to the third couplet [3, 3′].

3(1’). Palpal setae 4; usually 5 large and 5 small premental setae present; some setae on margin of frontal shelf spatulate (Fig. 391e) [erronea]
3’. Palpal setae 5-7; 5-9 large and 3-5 small premental setae present; all setae on frontal shelf slender, not spatulate (Fig. 391f) [4]

No. 2 | Cordulegaster sp. | exuvia (inner prementum)

(See a full-size version of the original photo, without annotation.)

The preceding annotated image shows the inner side of the prementum. Four (4) palpal setae are present, plus five (5) large- and five (5) small premental setae. The premental setae on the lower-right side of the prementum seem to be more intact than the ones on the upper-left: the large premental setae are labeled using white numerals; the small premental setae are labeled using red numerals.

The setae on the frontal shelf are mostly missing, as shown below. It’s possible they were broken off either when the larva burrowed in stream sediment (personal correspondence, Sue Gregoire) or when I cleaned the specimen.

No. 3 | Cordulegaster sp. | exuvia (frontal shelf)

(See a full-size version of the original photo, without annotation.)

Genus and species

The number of palpal setae strongly indicates the specimen is an exuvia from a Tiger Spiketail dragonfly (Cordulegaster erronea). Further, the rudimentary ovipositor shown in Photo No. 1 indicates this individual is a female.

The face behind the mask

Do you remember the way the female exuvia looked with its mask-like labium in place? In my opinion, she looked exotically beautiful!

No. 4 | Cordulegaster sp. | exuvia (face-head)

(See a full-size version of the original photo, without annotation.)

Well, that was then and this now. The following photo shows the face and mouth of the exuvia after the face mask was pulled away from the face in order to count the setae on the inner side of the prementum. Look closely at the full-size version of the photo. Yikes, that’s the stuff of nightmares!

No. 5 | Cordulegaster sp. | exuvia (face and mouth)

Tech Tips

The following equipment was used to shoot macro Photo No. 2, 3 and 5: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (set for 2x); and Canon MT-26EX-RT Macro Twin Lite. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for some photos.

The following equipment was used to shoot macro Photo No. 1 and 4Fujifilm X-T1 digital camera; Fujifilm MCEX-11 extension tube; and Fujinon XF80mm macro lens. An off-camera Fujifilm EF-X500 external flash unit and Sunpak LED-160 Video Light (with a white translucent plastic filter) were used for Photo No. 4. A Raynox DCR-250 close-up filter and Canon MT-26EX-RT Macro Twin Lite was used for Photo No. 1.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resource: Cordulegastridae exuvia, a blog post by Walter Sanford featuring an exuvia collected by Mike Boatwright.

Copyright © 2018 Walter Sanford. All rights reserved.

Tachopteryx thoreyi exuvia

February 14, 2018

A Gray Petaltail dragonfly (Tachopteryx thoreyi) exuvia was collected on 28 May 2017 by Mike Boatwright in Amherst County, Virginia USA. Gray Petaltail is a member of the Family Petaluridae (Petaltails).

The exuvia has a flat labium, similar to members of the Family Aeshnidae (Darners) and Family Gomphidae (Clubtails). Its seven-segmented antennae are thick and club-like, similar to Clubtail dragonflies.

No. 1 | Gray Petaltail (Tachopteryx thoreyi) | exuvia (face-head)

(See a full-size version of the original photo, without annotation.)

The specimen is ~3.5 cm long and  ~1 cm wide. The wing pads extend to the end of abdominal segment five (S5), as shown in Photo No. 2. The exuvia features two rows of dorsal hooks down its back.

(See a full-size version of the original photo, without annotation.)

Photo No. 3 shows a ventral view of the exuvia. Notice the “rudimentary ovipositor” located on abdominal segment nine (S9). An ovipositor is used for egg-laying by all adult damselflies and some species of adult dragonflies: females have this feature; males do not. Therefore, this individual is a female Gray Petaltail.

(See a full-size version of the original photo, without annotation.)

Tech Tips

The following equipment was used to shoot all of the preceding photographs: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tube; Canon EF100mm f/2.8L Macro lens (set for manual focus); and Canon MT-26EX-RT Macro Twin Lite. A Sunpak LED-160 Video Light (with a white translucent plastic filter) was used for some photos.

Adobe Photoshop CC 2017 was used to annotate selected images.

The Backstory

Mike Boatwright has steadfastly resisted my best efforts to lure him to the dark side of odonate exuviae collection and identification. As a concession to me, Mike kindly agreed to look-out for exuviae in unusual habitats. As it turns out, the first exuvia Mike collected for me is a prized specimen. Perhaps I should have titled this post “Mike strikes gold in Virginia!”

Image used with permission from Mike Boatwright.

“Beginner’s luck?” Nope. I know from firsthand experience Mike Boatwright is an extraordinarily keen-eyed odonate hunter. Way to go, Mike!

Related Resource

The dichotomous key for Petaluridae larvae that appears on p. 320 in Dragonflies of North America, Third Edition by Needham et al. is as follows.

1. Antennae 6-segmented, 3rd and 5th segments longer than wide (Fig. 381); cerci each more than 1/2 as long as epiproct; lateral margins of abdominal segments 3-9 not expanded, lateral spines inconspicuous; western [Tanypteryx (p. 322)]
1’. Antennae 7-segmented, 3rd and 5th segments not longer than wide (Fig. 379); cerci each less than 1/2 as long as epiproct; lateral margins of abdominal segments 3-9 expanded, lateral spines conspicuous; eastern [Tachopteryx (p. 321)]

Copyright © 2018 Walter Sanford. All rights reserved.

How to calculate magnification

February 12, 2018

By definition, a true macro photo is one with a magnification of at least one-to-one (1:1, or 1/1), that is, one unit on the camera sensor is equal to at least one of the same units in the real world. Magnification (in-camera) can be calculated using the following formula.

Mc = size of subject on camera sensor / size of camera sensor

Both measurements must be expressed in the same units in order for the units to cancel during division.

For example, let’s look at the following “full-size” image of a Corduligastridae erronea exuvia. “Full-size” means the image is uncropped (4896 x 3264 pixels).

The photograph shown above was taken using a Fujifilm X-T1 digital camera, Fujifilm MCEX-11 extension tube, and Fujinon XF80mm macro lens. The specifications for the macro lens lists the maximum magnification as 1x. Question is, what is the actual magnification of the subject?

The X-T1 features an APS-C sensor (23.6 mm x 15.6 mm). The dragonfly exuvia is approximately 35 mm in length, or 3451 pixels out of 4896 pixels across the entire image.

Using two equivalent ratios, the following proportion can be used to solve for the length of the exuvia on the camera sensor, in millimeters (mm).

x mm / 23.6 mm = 3451 pixels / 4896 pixels

x = ~16.6 mm. In other words, the exuvia is ~16.6 mm wide on a camera sensor that is 23.6 mm across.

Calculate the in-camera magnification using the following formula.

16.6 mm / 23.6 mm = ~0.7x

The magnification of the subject is ~0.7x, meaning the size of the subject on the camera sensor is slightly smaller than the width of the camera sensor. Expressed another way, the in-camera image is ~7/10 life size.

1.19x is listed as the theoretical maximum magnification using an MCEX-11 extension tube mounted on the 80mm macro lens. If we round the spec’d magnification to ~1.2x, then it’s clear that the actual magnification of ~0.7x is less than advertised, meaning the lens/extension tube combination is capable of focusing more closely on the subject than my sample photo.

Related Resources

Copyright © 2018 Walter Sanford. All rights reserved.

Cordulegastridae exuvia

February 6, 2018

My good friend Mike Boatwright, a fellow Virginian and extraordinarily good odonate hunter, collected an exuvia on 22 June 2017 in Amherst County, Virginia USA. Mike sent the exuvia to me for identification. This specimen is a member of the Family Cordulegastridae (Spiketails).

Photo No. 1 enabled me to see all of the critical field markers required to make an identification to the family level for this specimen. Here’s the decision tree I used to identify the exuvia as a spiketail dragonfly, based upon the excellent Vimeo video, Identifying dragonfly larva to family (8:06).

  • The specimen has a mask-like labium.
  • The margins of the labium have “deeply jagged, irregular teeth.”

Of the four families of dragonflies that feature a mask-like labium, the crenulations on the face of Corduligastridae are unmistakeable!

No. 1 | Cordulegaster sp. | exuvia (face-head)

(See a full-size version of the original photo, without annotation.)

The specimen is ~3.5 cm long (~1.4 in) and ~8 mm wide (0.3 in) at its widest. Notice the dorsal side of the exuvia is covered by sandy grit. The specimen will need to be cleaned in order to get a clearer view of the frontal shelf.

No. 2 | Cordulegaster sp. | exuvia (dorsal)

(See a full-size version of the original photo, without annotation.)

Photo No. 3 shows a ventral view of the exuvia.

No. 3 | Cordulegaster sp. | exuvia (ventral)

(See a full-size version of the original photo, without annotation.)

Photo No. 4 shows a closer view of the “rudimentary ovipositor,” located on abdominal segment nine (S9). An ovipositor is used for egg-laying by all adult damselflies and some species of adult dragonflies: females have this feature; males do not. Therefore, this individual is a female spiketail.

No. 4 | Cordulegaster sp. | exuvia (ventral, rudimentary ovipositor)

(See a full-size version of the original photo, without annotation.)

Photo No. 5 shows a closer view of the mentum, a two-segment hinged “jaw” that is used to grab food: the prementum is the segment of the labium closer to the mouth; the postmentum is the segment closer to the base of the head. Only the prementum can be seen in the following photo.

No. 5 | Cordulegaster sp. | exuvia (ventral, prementum)

Determining the genus and species

Although it’s easy to identify Cordulegastridae exuvia to the family level, it’s more challenging to identify a specimen to the species level. First, the exuvia must be cleaned in order to show the small hairs and brown dots on the frontal shelf. Second, the labium must be pulled forward to show the inside of the face mask in order to count palpal- and premental setae.

Tech Tips

The following equipment was used to shoot all of the macro photographs featured in this post: Fujifilm X-T1 digital camera; Fujifilm MCEX-11 extension tube; and Fujinon XF80mm macro lens. An off-camera Fujifilm EF-X500 external flash unit and Sunpak LED-160 Video Light (with a white translucent plastic filter) were used for Photo No. 1-3 and 5. A Raynox DCR-250 close-up filter and Canon MT-26EX-RT Macro Twin Lite was used for Photo No. 4.

Adobe Photoshop CC 2017 was used to annotate selected images.

Related Resources

Copyright © 2018 Walter Sanford. All rights reserved.

Have you ever wondered…?

January 9, 2018

Have you ever wondered…

The preceding photo shows the “focal plane mark” on my Fujifilm X-T1 digital camera.

The same mark appears on my Canon EOS 5D Mark II DSLR, as shown on p. 16 of the “Instruction Manual.”

Minimum focusing distance versus working distance

The “minimum focusing distance” is the distance from the subject to the focal plane. The “working distance” is the distance from the front of the lens to the subject.

For example, the minimum focusing distance for the Fujinon XF80mm macro lens (shown above) is 246 mm (24.6 cm). The working distance is 98 mm (9.8 cm).

Magnification (or magnification ratio)

True macro lenses have a magnification ratio of at least 1:1, meaning the size of the subject is the same size on the focal plane (digital sensor).

For example, the digital sensor for the Fujifilm X-T1 is 23.6 mm wide by 15.6 mm high. At a magnification ratio of 1:1, a subject that is 15 mm (1.5 cm) long will be 15 mm (1.5 cm) wide on the digital sensor; expressed another way, the subject will fill ~64% of the frame width.

For a prime macro lens, maximum magnification of 1:1 is possible only at the minimum focusing distance; magnification is necessarily lower at longer focusing distances.

Adding an extension tube

Adding a Fujifilm MCEX-11 extension tube reduces the working distance to 89 mm (8.9 cm). It’s interesting to note the minimum focusing distance of 249 mm (24.9 cm) is essentially the same, with or without the extension tube.

The net effect of adding an extension tube is the magnification ratio is increased to a value greater than 1:1, say 1.2:1, so the subject appears slightly larger on the focal plane.

Related Resource: Adding an 11mm extension tube, a blog post by Walter Sanford.

Copyright © 2018 Walter Sanford. All rights reserved.

More light diffusion

January 7, 2018

A toy dinosaur was photographed using a Canon MT-26EX-RT Macro Twin Lite mounted on a Canon EF 100mm f/2.8L Macro IS lens (set for manual focus), Kenko 20mm macro automatic extension tube, and Canon EOS 5D Mark II DSLR camera (set for manual exposure). Snap-on plastic light diffusers were mounted on both flash heads.

The first photo shows a wider view of the small plastic toy.

Default light diffusion on both flash heads (snap-on plastic diffusers).

The next photo shows a closer view of the same toy. Specular highlights are more noticeable when the flash heads are closer to the subject.

Default light diffusion on both flash heads (snap-on plastic diffusers).

More light diffusion was added by mounting four layers of translucent white plastic foam on the right flash head (facing forward). Notice the specular highlights are less glaring on the right side of the last photo than on the left.

More light diffusion added to right flash head (facing forward).

Copyright © 2018 Walter Sanford. All rights reserved.

Toys are for testing

January 5, 2018

The first photo shows a laid-back toy monkey, photographed using a Canon MT-26EX-RT Macro Twin Lite mounted on a Fujinon XF80mm macro lensFujifilm MCEX-11 extension tube, and Fujifilm X-T1 digital camera.

The Fujinon macro lens is tack sharp. Hotspots from the Canon macro twin lite, technically known as specular highlights, are visible in two regions of the monkey’s face. Although snap-on plastic light diffusers were used with both flash units, additional diffusion seems to be necessary.

The last two photos were taken using the same external macro flash unit mounted on a Canon MP-E 65mm Macro lens (set for 1x) and a Canon EOS 5D Mark II DSLR.

The preceding photo shows a rubber duck, SWAG from the Sleep Inn in Staunton, Virginia.

The following photo shows Totodile, a Pokemon character. Depth of field is noticeably very shallow. The focus point is the eye of the toy.

Copyright © 2018 Walter Sanford. All rights reserved.

Dragonflies and Damselflies (poster, slideshow)

January 3, 2018

 

D R A G O N F L I E S  A N D  D A M S E L F L I E S
HUNTLEY MEADOWS PARK

W A L T E R  S A N F O R D
Educator | Naturalist | Photographer

 

Copyright © 2018 Walter Sanford. All rights reserved.


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